The present invention relates to a position detecting apparatus for use in industrial robots.
In industrial robotics applications, there are instances where it is difficult to accurately position an object or workpiece to be machined or otherwise processed by an industrial robot. To cope with this problem, a position detector has been employed for gaining positional information of the workpiece.
One general type of such a position detector comprises an industrial camera, which requires a processing system having a sophisticated computing capability and is highly costly. Another position detector with a simplified processing system comprises a two-dimensional matrix of 2 by 2 photoelectric transducers. The image of an object is focused on the transducer matrix, and the detected signals from two adjacent photoelectric transducers are subtracted one from the other. If the focused object image is positioned intermediate between the two adjacent photoelectric transducers, then the difference d between the detected signals is expressed as d.apprxeq.0. If the image is located near the position between the two adjacent phototransducers, then the signal difference d is expressed as d&gt;&gt; 0 or d&lt;&lt;0. If the image is positioned otherwise, then the signal difference d meets the relationship: d.apprxeq.0. Based on this principle, the object can positionally be determined by employing a simple combination of logic circuits which detects when the difference d becomes 0 as it varies from d&gt;&gt;0 to d&lt;&lt;0.
However, the conventional position detector with two-dimensional 2 by 2 photoelectric transducers needs a two-dimensional scanning system for scanning the photoelectric transducers, and suffers from a requirement for an extended period of time required for the two-dimensional scanning operation.